1. Field of The Invention
The present invention relates generally to an electron gun for a color CRT (cathode ray tube ). Specifically, the present invention relates to a technique for correcting a spot shift amount for electron beams output by an electron gun of a color CRT.
2. Description of The Prior Art
In a color CRT it is preferable that a shift amount for spot movement of electron beams on a light receiving surface comes to zero. Spot shifting of electron beams is caused by geomagnetism, dimensional displacement of the electron gun in a thermal process, or the like. Conventionally, a magnetic shield plate is arranged on the CRT to minimize geomagnetic effects. However, spot shift due to other causes could not be prevented. New higher definition standards require that spot shift be held as low as possible to provide image stability and higher image definition.